<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .box{
            width: 200px;
            height: 100px;
            padding: 1em;
            border: 1px solid transparent;
            background: linear-gradient(white,white) padding-box,
                        repeating-linear-gradient(-45deg,
                        black 0,black 25%,white 0,white 50%)
                        .6em .6em ;
            animation: ants 3s linear infinite;
        }
        @keyframes ants{
            to {background-position: 100%}
        }
    </style>
</head>
<body>
    <div class="box"></div>
</body>
</html>